In the aircraft and other industries, lock bolt type fasteners are often used in order to provide a tight and secure connection between two elements. Such fasteners commonly have a collar that is swaged onto the shaft of the fastener for permanent attachment thereto. The collar cannot be removed without destroying the collar. Thus, the tightness and security of the connection is greater than can be obtained by the use of other types of fasteners, such as threaded fasteners with nuts, that can be removed without destroying any part of the fastener.
A commonly used type of lock bolt is the type sold by Huck Manufacturing Company of Carson, Calif. under the trademark HUCK. An example of this type of fastener 6 is shown in FIGS. 1 and 2. The fastener 6 has a head 8 formed at the outer end of a shaft portion, generally referred to as the "pin". The shaft portion extends along an axis X. At an axial midportion of the shaft or pin, a breakneck groove 13 is formed separating the permanent portion of the shaft from an inner breakoff portion 12. Parallel circumferential grooves 10 are formed on the shaft axially outwardly of the breakneck groove 13. The fastener 6 is held in position securing together two structures 2, 4 by a collar 14 made from aluminum or titanium. The portion of the collar 14 that abuts the inner surface of the structure 4 has a radial flange 16 formed thereon.
In order to install the fastener 6, the collar 14 is placed over the inner end of the pin 12 and is moved into position with the flange 16 abutting the inner surface of the structure 4. Then, a power operated tool pulls axially on the inner portion 12 of the pin to draw the structures 2, 4 together. As the pull on the pin 12 increases, an anvil portion of the tool swages the collar 14 into the circumferential locking grooves 10 to form a permanent lock. The tool continues to pull until the pin breaks at the breakneck groove 13 and the inner pin portion 12 is ejected. Finally, the tool anvil disengages from the swaged collar 14. The drawing together of the structures 2, 4 and the locking engagement of the collar material in the locking grooves 10 provide a tight and secure connection between the structures 2, 4. This connection is illustrated in FIG. 2.
The type of tight, secure connection provided by lock bolt fasteners, such as the fastener 6 shown in FIGS. 1 and 2, is required in a number of situations in the manufacture of aircraft. However, the illustrated fastening connection has the disadvantage of not being readily detachable when repair of one of the structures 2, 4 or adjacent components is required. The fastener 6 cannot be removed without removing the collar 14, and the collar 14 cannot be removed without destroying it. In some circumstances, the destruction of the collar 14 without damaging the structures 2, 4 is extremely difficult, if not impossible, using known methods. While, in most cases, damage to metallic structures is not a problem, structures made from other types of material are vulnerable to damage. One such type of material is fiber reinforced, resin matrix composite materials, such as graphite fiber reinforced epoxy resin plastics, which are being used increasingly in the manufacture of aircraft. Such materials are likely to be damaged if the collar 14 is subjected to an impact force sufficient to smash the collar 14 off the shaft of the fastener 6.
The applicants are aware of only four known methods of removing a collar 14 that comply with the high standards applicable to the manufacture and repair of aircraft. Two of these methods require access to the collar 14 from a vertical direction, i.e. from a direction parallel to the axis X of the fastener 6. One method is to use a bolt cutter which resembles hedge shears with short jaws and which cuts vertically along both sides of the collar 14 simultaneously. The other method uses an attachment to the type of tool used to install a lock bolt fastener, as described above, and has vertical blades which act in a manner similar to the bolt cutter blades. Both of these vertical methods may be used in situations in which the fastener 6 joins composite material structures. However, a major problem in many areas of an aircraft is the lack of space available, and the consequent lack of sufficient access to the collar 14 to approach it vertically. In such situations, a collar removing tool must engage the collar 14 in a horizontal direction, i.e. in a plane perpendicular to the axis X.
FIGS. 3 and 4 illustrate the only type of prior horizontal collar remover known to the applicants. The illustrated tool 20 has a forward end with end surfaces 24 on opposite sides of a slot 26. The slot 26 is sized to be very slightly wider than the diameter of the shaft of the fastener 6. In use, the front end surfaces 24 of the tool 20 are placed against the collar 14, as shown in FIG. 4. Then, the rear end 22 of the tool 20 is struck with a hammer to smash or shear the collar 14 off. The direction of the force of the hammer blow is essentially along the axis of the tool 20 and is indicated by the arrow in FIG. 4. The tool 20 shown in FIGS. 3 and 4 works well to remove an aluminum or titanium collar 14 and is acceptable for use when the structures engaged by the fastener 6 are metallic. However, the hammer impact force required is of a magnitude unacceptable for composite material structures 2, 4.
Currently, collars are being removed from lock bolt fasteners in situations involving composite materials by drilling the collars off. This approach has proved less than satisfactory. One major drawback is that the drilling procedure is relatively tedious and time consuming. Another major drawback is that the drill tends to slip off the collar 14 and damage the composite material. This leads to a need for more extensive repairs than were originally required and further increases the amount of time required for the repairs. In addition, drilling the collar off from a horizontal direction is impractical, and therefore the drilling must generally be done in a vertical direction.
Because of the significant limitations of the known methods of removing collars from lock bolt type fasteners, there is currently a great need in the aircraft industry for a tool that will reliably and consistently remove collars from lock bolts in limited access areas without damaging composite material structures joined by the lock bolts.